Method of making pattern



March 30, 1965 BREINING ETAL 3,175,259

METHOD OF MAKING PATTERN 3 Sheets-Sheet 1 Filed Oct. 5, 1961 INVENTORS ELMER ROBERT BRE/N/NG W/LBUR BOLTON ATTORNEYS March 30, 1965 BREINING ETAL 3,175,259

METHOD OF MAKING PATTERN Filed Oct. 5, 1961 I5 Sheets-Sheet 2 "ii I INVENTOR5 ELMER ROBERT BRE/N/NG W/LBUR M- BOLTON ATTORNEYS March 30, 1965 E. R. BREINING ETAL 3,175,259

METHOD OF MAKING PATTERN 3 Sheets-Sheet 3 Filed Oct. 5. 1961 INVENTORS ELMER ROBERT BRE/N/NG W/LBUR M QOLTON BY%M ATTORNEY 5 United States Patent M 3,175,259 METHOD OF MAKING PATTERN Elmer Robert Breining, Stockton, Calif., and Wilbur M.

Bolton, Piqua, Ohio, assignors to Union Carbide Corporation, New York, NY.

Filed Oct. 5, 1961, Ser. No. 143,155 '1 Claim. (Cl. 22195) This application is a continuation-in-part of applicants copending application, Ser. No. 767,841 filed October 17, 1958, now abandoned.

This invention relates to the manufacture by gas plating of self-supporting articles or structural shapes and the like, particularly pattern shapes having intricate contour surfaces which it is desired to be duplicated.

While the present invention is described and illustrated in the preparation of foundry patterns and the like shapes it will be obvious that other and various articles and shapes can be made by employing the same techniques as herein disclosed. In fact, the invention may be used in any instance where it is desirable to duplicate a shape by gas plating 'so as to obtain a self-supporting image of the shape.

The invention comprises gas plating of metal from a gaseous heat-decomposable'metal compound, and consists of providing a mold surface with a complementary pattern of the surface to be produced, heating the mold to a temperature such as will heat-decompose a gaseous metal compoundsuch as nickel carbonyl, and then bringing the gaseous metal compound in contact with the heated mold to cause the metal compound to be decomposed and the metal deposited on the mold surface.

After sufiicient metal has been deposited to provide a self-supporting layer of metal, and which is dull grey in color, the gas plated metal deposit is stripped away from the mold surface to provide a die having a working surface of substantially pure metal.

In the prior art disclosures, it was stated over seventy years ago in a British patent of Mond (767,841 of 1890) that molds, cores and surfaces of nickel could be made by initially coating the surface to be plated with graphite, coal dustor the like, to prevent the nickel deposit from sticking to the mold surface, and then immersing the graphite-coated mold surface in a solution of nickel carbonyl dissolved in benzol or the like petroleum solvent.

According to the British patent, nickel is said to deposit upon a mold surface immersed in the liquid at a temperature of 60 to 70 C., and upon surfaces which are exposed to the vapor at about 150 C. Further, the patentee states that bright deposits of nickel metal are produced. Tests conducted in the laboratory have shown conclusively that the only time a bright deposit of nickel is produced is in the initial flash coating. Such flash coatings do not measure more than a few millionths of an inch in thickness. It is not possible to obtain bright deposits of gas plated nickel when the metal is deposited to a thickness of five mils and over and such as required to produce self-supporting shapes in accordance with the present invention.

The prior British patent sets out that gases containing a small quantity of the nickel compound up to 5% produce a more uniform deposit of nickel than richer gases which the patent states are more apt to form rough surfaces. On the contrary, tests made in accordance with the present process, and observing the criterions as to velocity of plating gas and temperature of plating, excellent plating deposits are obtained employing a plating gas containing even 100% of the metal carbonyl. For example, it has been observed that where the gas plating of metal, e.g.

nickel is carried out using a plating gas containing only 5% nickel carbonyl is entirely unsatisfactory because the metal deposit obtained is a highly stressed, nonadherent 3,175,259 Patented Mar. 30, 1

and discontinuous metal structure. Furthermore, the deposition rate is less than 1 mil per hour which is undesirable. A satisfactory deposit requires a deposition rate of at least 5 to 20 mils per hour, and in some cases, e.g. copper wire thin metal coatings deposited at the rate of 200 mils per hour are readily obtained by the process of this invention.

In accordance with the present invention it has been discovered that the plating gas mixture must contain not less than 10% by volume of the metal carbonyl to produce self-supp0rting accurately reproduced shapes. This content of the metal compound in the plating gas is a criticality of the present process. Likewise the production of shapes of unlimited thickness, such as required for making foundry patterns, molds and dies, is carried out by gas plating using nickel carbonyl at a concentration to of the metal carbonyl. The velocity of the plating gas over the plating surface is held below 20.0 cm. per second. This velocity limitation is critical in order to produce satisfactory plating deposits.

Further, according to the prior disclosed process in the aforementioned British patent of Mond, it is stated that the molds used for preparing articles of nickel are put into an air-tight chamber in which they are heated to 200 C. It is our discovery, after conducting numerous test runs, that in the gas plating of nickel, employing nickel carbonyl, it is essential to carry out the plating below 392 F. (200 C.). Tests conducted in the laboratory as well as on a commercial scale have definitely proved that when temperatures are used which are substantially higher than the thermal decomposition temperature of nickel carbonyl such higher temperatures cause the carbonyl to decompose and drop the nickel as a fine powder which results in excessive bumpiness and forms rough surfaces in the metal deposit. Also gross nodule growth takes place at these higher temperatures.

In the British patent, the patentee further states that it is advantageous to heat the goods to be plated in a current of hydrogen to about 752 F. (400 C.) before taking them out, as by this treatment the nickel acquires great ductility. This statement in the patent makes it clear that utilizing the process described in this British patent that one will obtain only metal deposits which are extremely thin and highly stressed. Such metal deposits cannot be removed from the supporting object or even handled before they are stress relieved. On the other hand, the metal deposits made according to the present specification, as confirmed by test results, are stress-free and quite ductile. It has also beenpossible for the first time to make satisfactory deposits of A2 inch in thickness on a commercial scale without the formation of nodules, the metal deposit being substantially free of.

any plating stresses.

The present invention has eliminated for all practical purposes the difficulties heretofore encountered in gas plating metal deposits of substantial thickness and which are stress-free and ductile.

Employing the teaching of the earlier methods, as

readily produce intricate contour shaped objects by gas plating whereby a self-supporting image of the desired object is obtained. The resultant gas plated shapes which are composed of substantially pure metal as a deposit exhibit good ductility and unexpectedly high resistance to wear. The metal deposits are also of uniform density throughout and free from cracks, stress laminations and disfigurations. Metal deposits which are highly stressed,

brittle or of varying density throughout cannot be used satisfactorily for the production of self-supporting shapes.

A primary object of this invention is to provide a selfsupporting article or shape having the above noted characteristics and which consists essentially of metal deposited under controlled conditions from a heat-decomposable metal bearing compound. Such metal deposits are of high purity, and the metal which is deposited directly from a gaseous phase on the substrate surface, reproducessuch surface in every minute detail no matter how intricate.

A further object of the invention is to provide a novel method of forming foundry patterns by depositing on a preformed substrate or mold surface of appropriate contouur a deposit of gas plated metal. The metal deposit is so controlled as to provide a substantially perfect surface configuration, which is, of course, complementary to that of the substrate surface. In practicing the invention, the flow of the plating gas to various sections of the substrate or mold surface is regulated to provide a substantially uniform thickness or deposit over the surface area being plated. However, it is to be noted that some variation in the thickness of the gas plated metal deposit is permissible since accurate contour representation is the primary objective. The metal-deposited pattern itself may be backed for use in handling or to bolster the strength of thinner pattern areas.

In carrying out gas plating of metal to produce foundry patterns, molds and dies, and the like, or any shape to be duplicated, according to the gas plating method of the present invention, it has been repeatedly found by laboratory tests, and as now confirmed by the practice of the invention on a commerical scale, that the presence of liquid droplets or particles of nickel carbonyl in the plating chamber or in contact with the surface being plated must not be tolerated. Where liquid carbonyl is present and contacts the surface being gas plated the resultant deposit is in the form of laminated nodules and highly stressed thus making such metal deposits entirely unsuited for the production of foundry patterns and dies or other selfsupporting shapes.

The metal deposited working die surface has been found to provide a substantially perfect surface configuration which is complementary to that of the mold surface. After removing the gas plated metal mold or pattern and which accurately reproduces the shape and contours of substrate surface upon which the metal is deposited, the pattern or die may then be backed with a suitable reinforcing material to facilitate handling of the pattern.

In carrying out the process the substrate body prefer ably has a coeflicient of expansion approximating that of the metal deposited thereon to produce the pattern. The plating gas containing a controlled concentration of the thermally decomposable metal compound is brought evenly in contact with the substrate surface while the substrate is heated to a temperature suificient to bring about decomposition of the gaseous metal compound and deposition of metal on the substrate surface. The process produces a uniform thickness of the metal deposit over the substrate surface which is essential to pro vide a pattern of deposited metal having the desired strength and durability in use.

In the production of foundry castings heretofore it has entailed providing a pattern of wood or metal for making the mold into which molten metal is poured to form a casting. Such methods require much labor and the patterns are difiicult to reproduce. Utilizing the present invention, however, the making of molds and the accurate duplication of pattern shapes are readily accomplished without the expenditure of tedious labor and materials as heretofore used in foundry practice. In accordance with the gas plating methods of the present invention, intricate patterns and molds are readily produced which are wear resistant, dimensionally stable and which can be readily duplicated. This has not been possible to achieve by conventional methods.

The invention will be more fully understood by reference to the following detailed description, and accompanying drawings wherein FIGURE 1 is a schematic drawing illustrating an apparatus arrangement useful in the practice of the invention;

FIGURE 2 is a longitudinal view, partially in section, of the plating chamber of FIGURE 1;

FIGURE 3 is a front view of the plating chamber of FIGURE 1;

FIGURE 4 is an elevational view illustrating the pattern produced in accordance with the invention;

FIGURE 5 is a view in perspective, of a modified gas plating chamber for forming a switch box cover, the chamber being broken away and certain parts shown in section in the interest of clarity; and

FIGURE 6 is an exploded view in perspective of the finished switch box and substrate mold on which the metal is deposited to produce the box.

Referring to the drawings, and first initially to FIG- URE l, the numeral 1 designates a source of liquid carbonyl, such as nickel carbonyl. Conduit 2 having valves 3 and 4 connects the source 1 with a reservoir 5. The reservoir 5 has a cover 6 and a pressure gauge 7. A liquid level device 8, connected through valves 9 and 10 with the reservoir 5, is provided to indicate the level of liquid carbonyl in the reservoir.

The numeral 11 designates a conduit which is connected to a source of carbon dioxide; carbon dioxide flows into the conduit in the direction indicated by the arrow. Conduit ll communicates with conduit 12 having a valve 13 which connects the dioxide supply with the reservoir 5, to thereby provide a gas pressure above the liquid carbonyl within the reservoir.

The reservoir 5 communicates through conduit 14, valve 15 and conduit 16 with a flow meter 17 having a valve 18. The exhaust connection of the flow meter is to conduit 19, which communicates with a vaporizer 20. Accordingly liquid carbonyl is supplied to the vaporizer under gas pressure. Also carbon dioxide is supplied to the vaporizer with the liquid carbonyl through valve 21.

The numeral 22 indicates a water reservoir having a pump 23 and a motor 24 for the supplying of hot water through line 25 to the water jacket 26 around the vaporizer 20. The exhaust line of the vaporizer indicated at 27 communicates with a manifold 28 (FIG. 2) having branch line pipes 29, 30, 31. Pipe 29 is the largest in diameter, while pipe 30 is somewhat smaller, and pipe 31 is the smallest. Suitable pipe diameters, for example, are /8, A and inch. The purpose of such arrangement is to provide a substantially uniform flow from the manifold. It has been found that when all of the inlet pipes are of the same diameter, tendency develops for the gas plated metal to build up close to the outlet of pipe 31 and more heavily than at the other pipes.

The gas plating chamber itself comprises an inner box 32 and walls 33 and a cover 34 through which the pipes 29, 30 and 31 extend. Sand 35 is retained by wall 36 and also by wall 33 to provide against undue heat loss. A water jacket 37, to which more detailed reference will be made hereinafter, surrounds the plating chamber.

The plating chamber has a mass of metal 39 which supports the mold 38 and is in intimate contact with the mold. However, it is to be noted that the mold could be formed integral with the metal 39. The mold material preferably has a coefficient of thermal expansion closely approaching that of the gas plated metal to be deposited. Also the mold material is preferably non-porous, heat conductive and free of moisture.

Embedded in the mold metal 39 and electrically insulated therefrom are heating elements 40 supplied through heaters 41. As shown in the drawings, three heaters and trated.

The numeral 42 designates a viewing window in one end of the plating chamber, while the numeral 43 indicates a location for a multiple thermocouple outlet, and the numeral 44 designates the plating gas inlet.

The exhaust lines from the plating chamber are designated as 45 and 46 in FIGURE 1, the exhaust being effected through valves indicated at 47 and 48. The lines 45, 46 communicate with the heater 49, which itself exhausts to a burner 50 wherein combustible gases of the process are burned. It is to be noted that if desired such gases may be recovered in order to minimize loss of metallizing gas. However, very high efficiencies have been attained with the apparatus and procedure described herein, and for compactness of apparatus it has been found that it is desirable to simply burn the exhaust. Referring now to the heating system, it is to be noted that the water jacket 37 of the plating chamber communicates through conduit 51 with the vaporizer water jacket designated at 26. The exhaust of the water jacket 37 is through line 52 to a water heater 53, hot water being returned to the reservoir through line 54.

In the practice of the invention the surface temperature of the mold upon which the pattern 55 (FIG. 4) is formed is important in attaining substantial uniformity. In one specific instance, the temperature ranged over the length of the surface from about 360390 F. and good results were obtained. While the edges of the mold tend to lose heat more rapidly and to show a somewhat lower temperature, this is not a serious defect, for accurate reproduction of the mold configuration is still achieved. Thus the surface designated at 56 (FIG. 4) and the accurate reproduction of the contour of the mold is the important factor although the plated pattern body must have sufiicient metal over the whole area to permit removal from the mold without deformation.

In the modification illustrated in FIGURE 5, a gas plating arrangement is shown for producing switch boxes. A gas plating chamber 60 is provided similar as the arrangement illustrated by FIGURE 1, the same being hermetically sealed. The chamber 60 is provided with an inlet conduit 62 through which the plating gas is admitted to the gas plating chamber, and a pair of outlets 64 and 65 for the discharge of gases from the plating chamber.

A mold 67 composed of plaster of Paris, or the like, and such as may be produced by calcining gypsum until it is partially dehydrated. The plaster is m'med with graphite to form a mold from which the gas plated metal deposit can be readily released. A plaster mix comprising to 30% graphite by weight is suitable. Alternatively, use may be made of a plaster mold having a coating of graphite applied over the surface area on which the metal is deposited. This enables the finished plating to be readily removed from the substrate surface. The surface 70 of the plaster-graphite mold 67 is shaped to correspond to the switch box pattern 72 and which is formed by gas plating metal onto the substrate mold surface 70. The pattern 72, as formed by the deposited metal, is released from the plaster-graphite mold surface 70 as illustrated in FIGURE 6.

To provide for heating of the mold 67 and substrate surface 70, an electrical heating pad 74 is provided and which is disposed beneath the mold, as illustrated in FIG- URE 5. Solid copper rods 76 are positioned in the hollow interior cavity 77 of the mold 67, to hold and evenly distribute the heat throughout the mold. The rods 76 are heated by the resistance coil heater 79, the latter being disposed beneath the substrate surface 70 and in conjunction with the solid copper rods 76 serve to heat the substrate surface evenly and uniformly. Heat insulating material, as at 80 is arranged within the gas plating chamber 60 to protect surfaces which are not to receive plated metal. Further, to distribute the plating gas over the substrate surface a funnel-shaped nozzle 82 is employed. The plating gas is thus introduced into the gas 6 plating chamber and directed evenly over the substrate mold surface as indicated by the arrows in FIGURE 5.

An example of the production of a stamping die is illustrative of a method of practicing the invention.

Example 1 A switch box mold formed of plaster and having a light coating of graphite to facilitate release of the metal deposit was gas plated using gaseous nickel carbonyl. The plaster-graphite mold was placed in a chamber and nickel carbonyl gas passed through the chamber at the rate of approximately 42 liters per minute and using a carrier gas of carbon dioxide. The concentration, by volume, of nickel carbonyl in the carrier gas was maintained at about 23% Ni(CO) and the temperature of the mold surface being plated was held to approximately 345 F. The plating rate at the substrate surface heavy trim was a approximately 0.004 inch per hour.

Physical properties of the resultant gas plated metal deposit were at follows- Yield strength 79,000 p.s.i. Tensile strength 101,000 p.s.i. Elongation in 2" 17%. Reduction in area 22.8% Rockwell B hardness 95.

Example 2 In this instance a steel stamping pattern was produced by gas plating. The substrate area of the mold surface approximate 656 square inches. Plating gas consisting of 42 liters per minute by volume was introduced into the gas plating chamber. This plating gas consisted of carbon dioxide as carrier gas containing approximately 23% by volume of nickel carbonyl vapor. The substrate mold surface being plated was heated to about 323 F. and the plating of nickel metal was approximately 0.004 of an inch per hour.

Physical properties of the gas plated metal deposit were as follows- Yield strength 70,000 p.s.i. Tensile strength 92,500 p.s.i. Elongation in 2" 19%. Rockwell B hardness 100.

The contour surfaces formed on the mold substrate surfaces are very sharp and accurate in every minute detail. The relatively pure metal, as deposited by gas plating, thus forms the working surface. Accordingly slight variations in temperature which do not effect the pattern or Working surface formed may be tolerated. The pattern surface which is the complement of the mold surface is always smooth; the pattern surface may be optically bright or dull depending upon the brightness of the mold surface, which itself depends upon the nature of the mold material to some extent.

Test runs have also indicated that the temperature of the heated mass 39 or copper rods 76 must be considerably higher than the substrate or pattern surface gas plated with metal. For example, at a temperature of 360-390" F. on the substrate surface, the temperature of the heated mass 39 was 680 F. while the actual heating element temperature was about 1020" F.

To provide a pattern or mold plating deposit of considerable thickness, that is, up to about at least at the thickest point, requires generally a long period of continuous plating, on the order of a day. This plating must be continuous in order to avoid striations or laminations which would produce an inferior pattern.

The mold or substrate surface need not be lubricated generally, but if desired the same may have a light coating of graphite applied thereto. Further, the mold may be of any suitable heat conductive, non-porous material which is resistant to the temperature involved in the metallizing operation.

An important factor in the process and product of invention is the reproducibility of the pattern or mold configuration. A plurality of patterns of substantially identical contour may be readily formed by the gas. plating method of the invention. This becomes important in production line casting operations and where frequently a plurality of identical patterns are required.

Further, the gas plated pattern or mold body is readily maintained in repair whether of nickel or other gas plated metal. The interfacial pattern surface formed against the mold in the initial instance conforms exactly with the mold substrate surface plated on and is free of pitting and other irregularities.

The gas plated metal deposit of which the pattern, die or working surface consists is very pure and tough, a factor which militates against corrosive attacks and prolongs the pattern life. Generally the metal of the pattern is in excess of 99 percent pure metal; a small percentage of carbon, usually less than 0.5 percent, however, may be tolerated.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions and accordingly it is desired to comprehend such modifications Within this invention as may fall within the scope of the appended claim.

What is claimed is- A method of producing a self-supporting foundry pattern metal shape which comprises the steps of positioning a mold having a surface complementary to that of the pattern to be produced within a chamber with the said mold surface exposed, directing a stream of plating gas containing a heat-decomposable metal bearing gas in contact with said mold surface; said plating gas containing at least 10% by volume of a heat-decomposable metal bearing gas, heating the mold while in contact with said metal bearing gas to decompose the gas and to efiect the deposition of metal on the said mold surface, continuing the deposition of metal without interruption and at a plating rate of approximately 0.004 inch of metal per hour until a thickness of deposited metal is built up sufficient to make the metal self-supporting and suflicient in thickness to support a pattern working surface, and controlling the stream of metal bearing gas to provide a substantially uniform thickness of the desposited metal over the mold length, and removing the self-supporting pattern of gas plated metal from the mold, said mold being shaped from plaster and the surface lightly coated with graphite, the mold surface being heated to approximately 345 F. and subjected to a gaseous mixture of carbon dioxide and nickel carbonyl, said nickel carbonyl constituting at least about 23% by volume of the mixture, and the plating being carried out employing a plating gas velocity over the plating surface of below about 20.0 cm. per second.

References Cited by the Examiner UNITED STATES PATENTS 455,230 6/91 Mond 117-1072 XR 2,753,800 7/56 Pawlyk et al 22200 2,953,472 9/60 Nachtman et al. 117107.2 XR 2,994,297 8/61 Toulmin 22-193 XR 3,024,506 3/62 Trimble 22193 XR FOREIGN PATENTS 21,025 Great Britain of 1890 OTHER REFERENCES Powell, Campbell and Gonser: Vapor Plating, pages -62, published 1955.

WILLIAM J. STEPHENSON, Primary Examiner.

MARCUS U. LYONS, MICHAEL V. BRINDISI,

Examiners. 

